For example, Japanese Patent Application Laid-Open Publication No. 2002-217935 (Patent Document 1) describes a method in which, in a stackable switching hub having a plurality of switching hubs connected via stack ports, a device ID number of each switching hub is set without having a management circuit mounted thereon. Japanese Patent Application Laid-Open Publication No. 2007-124673 (Patent Document 2) describes a method in which, in a stack type switching system in which a plurality of units operating as a master and slaves are connected via stack ports, a unit having the highest priority order is made to operate as a master on the occasion of the change of a topology design configuration.